Before Adam Lanza walked into Sandy Hook Elementary School on Friday morning and murdered 20 children and six adults, my sister was already a teacher on edge and in mourning. The night before, in the parking lot of her high school in the Pacific Northwest, a 16-year-old student from her first-period class shot and killed himself. Three months earlier, her school had been forced to close for a day after a former student made a threat on social media to “open fire on people in the commons in the morning until I am either taken down by the school’s police officer, or until I run out of [ammunition].”

He was arrested before he could do any harm. Still, my sister’s experiences are one more reminder of the outsize specter gun violence has become for educators. Rampage killers target schools in order to deliver that worst-of-all blow to society’s gut, the massacre of children. But I’ve covered a number of school shootings, starting with Laurie Dann’s 1988 spree at Hubbard Woods Elementary School outside Chicago, and I’m all too aware of a daunting reality that confronts teachers like my sister — and my wife and my mother. On the one hand, they’re as vulnerable as their pupils; on the other hand, they’re the only first line of defense between kids and killers.

That was the case at Sandy Hook, where teachers were credited with quick thinking that saved children’s lives. Administrators are under increasing pressure today to put metal detectors and other expensive measures in place that we think will keep armed monsters out of our schools. But as we saw at Sandy Hook, which had recently ramped up its security infrastructure, they hardly make schools impregnable — and school shootings, meanwhile, seem to have become as frequent as science fairs. Which, as long we lack the national spine to confront the gun lobby, raises a depressing but urgent question: Is shielding children now as essential a part of teachers’ portfolios as educating children is? If so, are we training teachers as effectively as we should to keep both students and themselves out of the line of fire — or even step up and confront their attackers — until the SWAT team arrives?

The core of the preparation teachers have increasingly been getting since the 1999 Columbine massacre is the lockdown drill — and Sandy Hook teachers, like those who reportedly scanned the hallways and swiftly pulled wandering students into their classrooms, had obviously been exposed to it. The procedures that schools like my sister’s and my wife’s have in place are much more involved than fire drills, and they would seem effective. A code alert from the principal’s office, usually via a PA system; the hallway scan, followed by locking doors and covering door windows; turning out lights while herding students into a corner or closet away from windows and telling them to stay silent; then sending e-mail alerts accounting for students who might be in the bathroom or some other area.

My sister’s principal, a woman who has put a lot of careful thought into this matter — to the extent that she doesn’t post on her high school’s website any school-building maps that potential attackers could study — tells me it’s largely about conditioning teachers “to know where everything is in every climate they inhabit at a school.” And I’ll second her assertion that teachers are willing to master civil defense along with pedagogy “because they go into this profession in the first place to make the world better for kids.”

But while the lockdown approach works well when you’ve got kids sitting in front of you, it’s less operative when a school’s occupants are scattered about— meaning a big part of the day. What’s the procedure when a gunman appears, Grendel-like, while students are exposed in the open: changing classes, eating lunch or ambling to the library like ducklings following a mother mallard? Even when students are gathered in class, a gunman can often move faster than the lockdown sequence, which is why Lanza was able to massacre 20 first-graders — and a teacher who only had enough time to throw herself in front of her kids — in two classrooms. So how, at all, do we train teachers and staff to respond when lockdown isn’t applicable?

Should teacher orientation include the sort of counterterrorism training we give flight crews today? My sister points out that few if any school systems would assume the legal liability of instructing teachers how to disarm or subdue a shooter. Don’t be a hero, school boards tell them by default. And yet, from Hubbard Woods to Sandy Hook, the raw heroism of teachers — who, like Sandy Hook principal and Lanza murder victim Dawn Hochsprung, did confront attackers — has saved countless lives, often by buying everyone else time to hide or escape. When teachers have no recourse, should we give them more to draw on than adrenaline?

My first instinct is to say no. Flight crews accept security as a central part of their job, but we’re stepping into very dark territory as a society when we expect teachers to be Navy SEALs. And I’m certainly disturbed when politicians — like U.S. Representative Louie Gohmert of Texas, who this weekend suggested that Hochsprung should have “had an M-4” rifle in her office — propose that teachers pack heat. Then again, the only alternative we might have at this point is to post the educational equivalent of an armed air marshal in every school. Why shouldn’t my wife and her second-graders enjoy the same peace of mind that I and my fellow airline passengers do?

My wife, sister and mother are three of the best teachers in the business. Yet here they are again this weekend, like millions of their colleagues, pondering not how to edify their students but how to shelter them. It’s not what they signed up for — but it’s what the rest of us are now going to have to sign up to solve.